Hello, We want to use ceph as the openstack storage system and we can afford a purely SSD based storage system. So we are planning to just setup meta data on SSD and leave the data on HDD The documentation around this isn't very clear and wonder if someone can explain a bit Here is what the documentation say:- https://docs.ceph.com/en/reef/start/hardware-recommendations DB/WAL (optional) 1x SSD partion per HDD OSD 4-5x HDD OSDs per DB/WAL SATA SSD <= 10 HDD OSDss per DB/WAL NVMe SSD What does this mean? I am sorry to say, but it look a tad ambiguous to me, but suspect its obvious once one have experience. I have 6 8TB disk per system, and I want to use replication so will end up with 18 OSD I am hoping I don't need 18 SSD as we don't even have enough bays If we can add in 2 800GB SSD per hardware, how do we optimally map those 18 DW/WAL to a total of 6 SSD disks? Regards, William